Clutch control valve for an automatic transmission control circuit

Abstract

A clutch pressure modifier valve for an automatic control circuit for a power transmission mechanism in a vehicle driveline wherein provision is made during ratio changes that requires engagement of a fluid pressure operated transmission clutch for modifying a clutch engagement pressure to compensate for the effect of centrifugal pressure build up in the pressure chamber of the clutch structure due to rotation of the clutch at high speeds during a shift interval whereby the timing of the clutch engagement is relatively independent of the rotary speed of the clutch during engagement and whereby the torque capacity of the clutch more closely matches the torque requirements of the driveline during ratio changes.

Having thus described preferred embodiments of our invention, what we claim and desired to secure by U.S. Letters Patent is: 
     
       1. In an automatic power transmission mechanism having relatively movable gear elements that define plural torque delivery paths between a driving member and a driven member; a fluid pressure operated clutch adapted to connect two torque delivery elements of said driveline together to effect a torque ratio change;   a fluid pressure source, conduit means including a high pressure portion connecting for pressure source to said clutch and including also a shift valve for distributing fluid pressure to and for exhausting fluid pressure from said clutch; and   an accumulator valve means in communication with a portion of the conduit structure that communicates with the clutch for delaying and cushioning the application of the clutch upon movement of the shift valve to effect clutch engagement and a pressure modifier valve means communicating with said high pressure portion of said conduit means for establishing a modulated pressure;   said pressure modifier valve means being in communication with said accumulator valve means whereby the latter is subjected to the modulated pressure to change the calibration of the accumulator valve means whereby it compensates for the effect of a centrifugal pressure build up in said clutch.   
     
     
       2. In an automatic power transmission having relatively movable gear elements that define plural torque delivery paths between a driving member and a driven member; a fluid pressure operated clutch adapted to connect two torque delivery elements of said driveline together to effect a torque ratio change;   a fluid pressure source, conduit means including a high pressure portion connecting the pressure source to said clutch and including also a shift valve for distributing fluid pressure to and for exhausting fluid pressure from said clutch;   an accumulator valve means in communication with a portion of the conduit structure that communicates with the clutch for delaying and cushioning the application of the clutch upon movement of the shift valve to effect clutch engagement and a pressure modifier valve means communicating with said high pressure portion of said conduit means for establishing a modulated pressure.   said pressure modifier valve means being in communication with said accumulator valve means whereby the latter is subjected to a modulated pressure to change the calibration of the accumulator valve means whereby it compensates for the effect of a centrifugal pressure build up in said clutch; and   fluid pressure governor valve means connected to driven portions of said transmission for developing a pressure signal that is related proportionally to the speed of said driven member;   said governor valve means being in fluid communication with said modifier valve means whereby the modulated pressure established by said modifier valve means is changed upon a change in driven speed so that the rate of pressure build up during a shift interval is reduced during a ratio change at high speeds to compensate for the effect of the centrifugal pressure build up in said clutch.   
     
     
       3. The combination as set forth in claim 1 wherein said accumulator means comprises an accumulator piston movable in an accumulator cylinder and spring biased in one direction, the clutch being in fluid communication with said cylinder on one side of said piston whereby clutch pressure opposes the forces of said spring and causes said piston to stroke upon an increase in clutch pressure; a flow restricting orifice in said circuit between said clutch in the other side of said piston; and   a capacity modulator valve for controlling the rate of flow of fluid through said orifice.   
     
     
       4. The combination as set forth in claim 2 wherein said accumulator means comprises an accumulator piston movable in an accumulator cylinder and spring biased in one direction, the clutch being in fluid communication with said cylinder on one side of said piston whereby clutch pressure opposes the forces of said spring and causes said piston to stroke upon an increase in clutch pressure; a flow restricting orifice in said circuit between said clutch in the other side of said piston; and   a capacity modulator valve for controlling the rate of flow of fluid through said orifice.   
     
     
       5. The combination as set forth in claim 2 wherein said pressure modifier valve comprises a valve chamber, a valve spool slidably received in said valve chamber and communicating with said high pressure portion of said conduit means and an exhaust port communicating with said valve chamber; spring means for biasing said valve spool in one direction, the modulated pressure developed by said pressure modifier valve acting on said valve spool to establish a pressure force that opposes the force of said spring and a governor land on said valve spool in communication with said governor valve means thereby developing a pressure force that complements the force of said spring;   the modulated output pressure of said pressure modifier valve acting on said accumulator valve means to oppose the force of the spring acting on said accumulator valve means.   
     
     
       6. The combination as set forth in claim 3 wherein said pressure modifier valve comprises a valve chamber, a valve spool slidably received in said valve chamber and communicating with said high pressure portion of said conduit means and exhaust port communicating with said valve chamber; spring means for biasing said valve spool in one direction, the modulated pressure developed by said pressure modifier valve acting on said valve spool to establish a pressure force that opposes the force of said spring and a governor land on said valve spool in communication with said governor valve means source thereby developing a governor pressure force that complements the force of said spring;   the modulated output pressure of said pressure modifier valve acting on said accumulator valve means to oppose the force of the spring acting on said accumulator valve means.   
     
     
       7. The combination as set forth in claim 4 wherein said pressure modifier valve comprises a valve chamber, a valve spool slidably received in said valve chamber and communicating with said high pressure portion of said conduit means and exhaust port communicating with said valve chamber; spring means for biasing said valve spool in one direction, the modulated pressure developed by said pressure modifier valve acting on said valve spool to establish a pressure force that opposes the force of said spring and a governor land on said valve spool in communication with said governor valve means source thereby developing a pressure force that complements the force of said spring;   the modulated output pressure of said pressure modifier valve acting on said accumulator valve means to oppose the force of the spring acting on said accumulator valve means.   
     
     
       8. The combination as set forth in claim 4 wherein said governor valve means comprises a governor pressure booster valve means for augmenting the magnitude of said governor pressure thereby making the accumulator more sensitive to speed and increasing the compensation for centrifugal pressure build up during shift intervals under higher torque. 
     
     
       9. The combination as set forth in claim 5 wherein said governor valve means comprises a governor pressure booster valve means for augmenting the magnitude of said governor pressure thereby making the accumulator more sensitive to speed and increasing the compensation for centrifugal pressure build up during shift intervals under higher torque. 
     
     
       10. The combination as set forth in claim 4 wherein said governor valve means includes a governor limiter for interrupting distribution of governor pressure to said pressure modifier valve at driven speeds of said driven member less than a selected value. 
     
     
       11. The combination as set forth in claim 5 wherein said governor valve means includes a governor limiter for interrupting distribution of governor pressure to said pressure modifier valve at driven speeds of said driven member less than a selected value.